The present invention relates to a method for forming a semiconductor device and, more particularly, to a method for forming contact hole in a semiconductor device.
Generally, a contact hole for an electric connection of a lower layer and an upper layer is provided in the semiconductor fabricating method and a plug, a landing plug, a bit line and a storage node are buried in the contact hole. In dynamic random access memory (DRAM) fabricating processes, the contact holes are formed in specific places in a cell region or a peripheral circuit region. Particularly, a bottom critical dimension of a wide contact region which is required to reduce the contact resistance in the cell region is very important.
However, when the develop inspection critical dimension (DICD) is increased in order to secure the bottom CD, the top CD is also increased so that there is a problem in that a bridge is caused by a slight misalignment between an upper contact and a lower contact at the subsequent processes to form another contact.
FIG. 1 is a schematic view illustrating a bridge between a lower contact and an upper contact in a typical semiconductor device. In FIG. 1, a lower contact is a bit line contact and an upper contact is a storage contact. The reference numeral “A” denotes an active region and “SNC” does a storage node contact hole. Also, the reference numeral “BLC” denotes a bit line contact hole.
Referring to FIG. 1, with the increase of the DICD in the formation of a bit line contact hole (BLC), the top CD is also increased. Accordingly, even though a little misalignment is caused when forming a storage node contact hole (SNC) at the subsequent processes, a bridge “B” is generated between the bit line contact and the storage node contact.
Moreover, in the typical method for forming the bit line contact, a buffered oxide etchant (BOE), which is used for a pre-cleaning process before the deposition of a bit line barrier metal layer, makes the top CD be wider so that the generation of the bridge is further increased between the bit line contact and the storage node contact.